Working Principle and Construction of Hot Air Oven

Meme

Introduction:

Hot Ar Oven is an instrument used for sterilization. It is the process or a method used to kill the microorganisms. The sterilization methods allows us to conduct contamination free experiments. When heat, radiation or such physical agents are used for sterilization, it is called as Physical methods of sterilization. Whereas the methods in which chemical agents are used are called as Chemical methods of sterilization. The use of Autoclave and Hot air oven instruments falls in physical methods of sterilization.

The heat kills the bacteria by denaturing the essential proteins and enzymes. It alters the permeability of membranes causing change in optimal concentrations of ions.

If the material, glasswares and items used in the laboratory are good conductors of heat then they serves to be an ideal for heat sterilization. Because when such material are exposed to heat, their outer surface absorbs the heat first and then transfer it to next internal layer. This assures the maximum sterilization. The use of heat for sterilization was initiated by Louis Pasteur.

Working Principle:

Hot Air Oven is an electrical devise that works on Heat convection principle. It consist of electrical heating coil that produces dry heat. In the chamber, the produced dry heat air displaces the cooled air forming heat gradient. The use of fan allows to the uniform distribution of heat. The Hot Air Oven is usually set at following temperature and for mentioned time-

170°C (340°F) for 30 minutes
160°C (320°F) for 60 minutes
150°C (300°F) for 150 minutes

Construction of Hot Air Oven:

Physically it appears similar to Incubator.

Cabinet: The cabinet body is made is up of stainless steel. The cabinet is coupled with insulator that does not allow heat to escape and hence maintains the temperature.

Shelves: The cabinet space is divided by the shelves, which provide space for placing the microbial culture.

Door: The Incubator looks like small cupboard, which has insulated door with handle. The Door is air tight because of asbestos gasket that allows keeping heat trapped inside the incubator.

Thermostat: It plays important role in maintaining the desired temperature. Thermostat contains the censor that senses the temperature and maintain as per the setting.

Control panel: The control panel is placed on the front side of the cabinet, just above the door. The control panel contains switches for all the parameters. We can set the parameter as per our need.

Hot Air Oven
https://link.springer.com/protocol/10.1007/978-1-4939-9861-6_5

Application of Hot Air Oven

The heat resistant material like glasswares, forceps, scalpel, scissors, syringes etc are sterilized using Hot Air oven.

Advantages:

  1. It is Eco-friendly
  2. It is most efficient method to degrade microbial endotoxins.
  3. It is safer than autoclave.
  4. It is the ideal instrument for sterilizing oil and powders.

Disadvantage

  1. It is time consuming because the dry heat penetrate slowly as compared to moist heat.
  2. It may not be efficient to degrade prions.
  3. The heat sensitive or heat labile material cannot be sterilized.
  4. It cannot be operated without electricity.

References:

https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3340325

http://universe84a.com/hot-air-oven/

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